<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>jQuery</title>
</head>
<body>
    <u1>
        <li>我是Li1</li>
        <li>我是Li2</li>
        <li>我是Li3</li>
    </u1>
</body>
<script src="./js/jquery.js"></script>
<script>
    $("li").click(function() {
        $(this).css("background","red")
    })
</script>
</html>